'72 6 cyl carb/vacuum advance solenoid question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

grancuda · 12-01-2008, 09:39 PM

I have been tuning on my '72 making it run really smooth. I replaced the cap, rotor, wires, plugs, points, condenser, fuel filters and rebuilt the carb, a mono jet. The truck is all stock and when I got it a year ago it had only 62,000 on it and now it has 87,000. Question is, I had a vacuum leak and it ended up being the solenoid on the carb that provides vacuum to the vacuum advance. I bypassed the solenoid and connected the vacuum advance directly to the carb and it seems to run fine now. Also, I hooked a vacuum pump/gauge to the vacuum line on the air cleaner that goes to the base then to the cod air door and it wouldn't pull any vacuum so I disconnected it and plugged the port at the base of the carb. It now revs very good and is a lot more responsive and has a lot smoother idle. Does anyone know what the solenoid is called to get another one or is it even needed? Also should I try and get the cold air damper working on the air cleaner/are the parts even avaliable?

Brad · 12-03-2008, 12:35 PM

My carbs never had a vacuum solenoid, but my Camaro has an idle stop solenoid. That's basically an anti-dieseling device. I've not had any luck in finding one the last few years as they're really not needed anyway. It doesn't sound like this is what you're looking for anyway. As far as the air cleaner vacuum thingy, the only advice I can give you is to check your LAPS. Fwiw, I don't think that part is critical, however I've replaced it on my Camaro about 15 years ago.

Perhaps you can post pics for more responses...

airdale94 · 12-03-2008, 01:56 PM

The vac. adv. should be hooked up to ported vac. It could have been run through a themal vac. switch but that would have been in the intake man.

grancuda · 12-03-2008, 02:30 PM

here are some pics

**john** · 12-03-2008, 02:41 PM

I haven't seen a six cyl. setup before, but I think that solenoid is yout TCS (trans controlled spark) . This only allows vacuum advance in high gear. Smog control. Most people unhook it.

68gmsee · 12-03-2008, 02:54 PM

Some states are pretty persnickity about disconnecting lines and hoses on your vehicle, but if I remember correctly you don't have to have an inspection on your vehicle in Oklahoma.

I have a 250 with single barrel Rochester. It has three vacuum ports, engine and ported, and an extra one?? that was plugged. I bought the truck bone stock from a friend whose dad owned it (orginally 26K miles).

Bottom line: Mine didn't come with any of the extras that you have and probably all you need is the vacuum for the advance. However, I would keep all of the other extra stuff just in case some new law comes into effect or some lawman checks your truck out.

edit: actually only 2 vacuum ports on carb. (had a brain burp)

Botietruck · 12-03-2008, 06:47 PM

Not sure about the carb solenoid, but the vacuum device on the air cleaner snorkel is called a "motor", and I purchased one from NAPA several years ago.

airdale94 · 12-04-2008, 09:18 PM

I would think the bottom port would be full. And if the other is higher up ported. Not exactly sure what that solenoid is doing differently than ported vaccum would do, probably emission related. I would just leave as is. You would basically be throwing good money at a bad design. In my "opinion".

Not necessarally a bad design on the heated air, just maybe not worth spending alot of money on.

12-01-2008, 09:39 PM	#1
grancuda Registered User Join Date: Nov 2007 Location: Central OK Posts: 396	'72 6 cyl carb/vacuum advance solenoid question I have been tuning on my '72 making it run really smooth. I replaced the cap, rotor, wires, plugs, points, condenser, fuel filters and rebuilt the carb, a mono jet. The truck is all stock and when I got it a year ago it had only 62,000 on it and now it has 87,000. Question is, I had a vacuum leak and it ended up being the solenoid on the carb that provides vacuum to the vacuum advance. I bypassed the solenoid and connected the vacuum advance directly to the carb and it seems to run fine now. Also, I hooked a vacuum pump/gauge to the vacuum line on the air cleaner that goes to the base then to the cod air door and it wouldn't pull any vacuum so I disconnected it and plugged the port at the base of the carb. It now revs very good and is a lot more responsive and has a lot smoother idle. Does anyone know what the solenoid is called to get another one or is it even needed? Also should I try and get the cold air damper working on the air cleaner/are the parts even avaliable?

12-03-2008, 12:35 PM	#2
Brad Out of the carpool lane. Join Date: Jan 2000 Location: Clark Co, WA Posts: 5,672	Re: '72 6 cyl carb/vacuum advance solenoid question My carbs never had a vacuum solenoid, but my Camaro has an idle stop solenoid. That's basically an anti-dieseling device. I've not had any luck in finding one the last few years as they're really not needed anyway. It doesn't sound like this is what you're looking for anyway. As far as the air cleaner vacuum thingy, the only advice I can give you is to check your LAPS. Fwiw, I don't think that part is critical, however I've replaced it on my Camaro about 15 years ago. Perhaps you can post pics for more responses... __________________ 1968 C-10 SWB, 5.7 Vortec/700R4/3.73 posi, Torch Red 1968 Camaro, 250/Powerglide, all original (No, I'm not gonna drop a 350 in it!...Jeez!) 2000 Honda VFR in the faster yellow! 2008 Husqvarna TE-610 1967 C-10 SWB 'Six Appeal'-Gone but not forgotten... Last edited by Brad; 12-03-2008 at 12:36 PM.

12-03-2008, 01:56 PM	#3
airdale94 Registered User Join Date: Jan 2007 Location: Topeka,KS Posts: 778	Re: '72 6 cyl carb/vacuum advance solenoid question The vac. adv. should be hooked up to ported vac. It could have been run through a themal vac. switch but that would have been in the intake man.

12-03-2008, 02:30 PM	#4
grancuda Registered User Join Date: Nov 2007 Location: Central OK Posts: 396	Re: '72 6 cyl carb/vacuum advance solenoid question here are some pics Attached Images

12-03-2008, 02:41 PM	#5
john member #16 Join Date: Dec 1999 Location: Yuba City Ca. Posts: 3,618	Re: '72 6 cyl carb/vacuum advance solenoid question I haven't seen a six cyl. setup before, but I think that solenoid is yout TCS (trans controlled spark) . This only allows vacuum advance in high gear. Smog control. Most people unhook it. __________________ john http://67-72chevytrucks.com/vboard/showgroups.php board vendors http://www.flickr.com/photos/1745471...7602865984234/

12-03-2008, 02:54 PM	#6
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: '72 6 cyl carb/vacuum advance solenoid question Some states are pretty persnickity about disconnecting lines and hoses on your vehicle, but if I remember correctly you don't have to have an inspection on your vehicle in Oklahoma. I have a 250 with single barrel Rochester. It has three vacuum ports, engine and ported, and an extra one?? that was plugged. I bought the truck bone stock from a friend whose dad owned it (orginally 26K miles). Bottom line: Mine didn't come with any of the extras that you have and probably all you need is the vacuum for the advance. However, I would keep all of the other extra stuff just in case some new law comes into effect or some lawman checks your truck out. edit: actually only 2 vacuum ports on carb. (had a brain burp) Last edited by 68gmsee; 12-03-2008 at 03:08 PM.

12-03-2008, 06:47 PM	#7
Botietruck '71 chevy s.bed/s.side Join Date: Mar 2005 Location: Chesapeake, VA Posts: 1,571	Re: '72 6 cyl carb/vacuum advance solenoid question Not sure about the carb solenoid, but the vacuum device on the air cleaner snorkel is called a "motor", and I purchased one from NAPA several years ago. __________________ STILL PLAYS WITH CARS...AND TRUCKS!! Parents! Be good to your kids...they get to choose your nursing home! 250 I-6 with a 3 speed Saginaw and Borg Warner Overdrive...She's got overdrive!

12-04-2008, 09:18 PM	#8
airdale94 Registered User Join Date: Jan 2007 Location: Topeka,KS Posts: 778	Re: '72 6 cyl carb/vacuum advance solenoid question I would think the bottom port would be full. And if the other is higher up ported. Not exactly sure what that solenoid is doing differently than ported vaccum would do, probably emission related. I would just leave as is. You would basically be throwing good money at a bad design. In my "opinion". Not necessarally a bad design on the heated air, just maybe not worth spending alot of money on.



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